1. Field of the Invention
The present invention relates generally to power distribution machinery and, more particularly, to circuit interrupters. More specifically, the present invention relates to an exhaust control device for use with a circuit interrupter.
2. Description of the Related Art
As is understood in the relevant art, numerous types of circuit interrupters are known and are employed for various purposes including the protection of electrical circuits. Among the various types of circuit interrupters are circuit breakers and fuses. Circuit breakers are more or less permanent components of an electrical circuit since they can be easily returned to an xe2x80x9conxe2x80x9d condition to permit the flow of current therethrough after a condition which has caused the circuit breaker to trip has been removed from the circuit. In contrast thereto, fuses typically must be replaced after the occurrence of an electrical event which causes the fuse to perform its circuit protection function.
Fuses generally include some type of fusing conductor that fuses or melts in the event of one or more certain specified conditions from which a circuit is desired to be protected. Fuses that are employed in medium voltage circuits such as 17 kV, 27 kV, 38 kV, and higher must be specially designed to extinguish any arcs that may propagate between the conductors that had previously been electrically connected with one another via the fusing element. One type of high voltage fuse employs a loaded spring connected with an arcing rod that cooperate to elongate the arc through a boric acid chamber upon melting of the fuse element. At high temperatures, boric acid disassociates and produces a blast of water vapor and inert boric anhydride. Electrical interruption is caused by the steam extinguishing the arc as the arc is being elongated through the cylinder. High particle turbulence of the boric acid products causes the rate of deionization within the fuse to exceed the ionization of the electrical arc, which results in rapid extinction of the arc. However, the blast of water vapor and boric anhydride exits the fuse at an extremely elevated temperature and velocity and thus has the capacity to burn materials in the immediately surrounding environment and additionally results in a loud noise.
As such, it is known to provide an exhaust control device through which the blast of water vapor and boric anhydride must pass before being discharged into the environment. Such exhaust control devices typically have included deionizing heat sinks and dampers of various configurations that reduce the temperature and the velocity of the blast gases prior to their discharge into the atmosphere. One example of such an exhaust control device is a muffler.
While such exhaust control devices have been generally effective for their intended purposes, such exhaust control devices have not, however, been without limitation. As is understood in the relevant art, such exhaust control devices can theoretically be configured to be sufficiently large and complex to reduce the temperature of the exiting gases to be near ambient temperature and can reduce the velocity of the blast gases to near zero. However, such a hypothetical exhaust control device would be extremely expensive to produce and would occupy an unduly large space. Moreover, it is necessary only to reduce the temperature, velocity, and ionization level of the blast gases to levels that make the blast gases less harmful to the surrounding environment. It is thus desired to provide an exhaust control device that is relatively small and inexpensive to manufacture yet reliably reduces the temperature and velocity of the exiting gases to non-dangerous levels. It is thus preferred that such an exhaust control device maximize the efficiency with which its heat sink and damper operate on the blast gases passing therethrough. Such an improved exhaust control device preferably would include multiple expansion chambers that would reduce the peak intensity of the blast within the exhaust control device and extend the duration over which the heat sink and the damper can remedially operate on the blast.
In view of the foregoing, an exhaust control device for use with a circuit interrupter includes a casing having a first expansion chamber and a second expansion chamber that are operationally disposed upstream of a heat sink and a damper, with the second expansion chamber being in fluid communication with the first expansion chamber and being in register with an inlet of the casing. The first expansion chamber extends generally between the inlet and the heat sink. The heat sink is a porous member that is generally annular in cross-section and includes a central cavity formed therein, the second expansion chamber being generally disposed in the central cavity. The first and second expansion chambers are advantageously configured to separate a blast of gases from the circuit interrupter into a first pressure wave and a second pressure wave that sequentially travel through the heat sink and the damper, which reduces the peak intensity of the blast, extends its duration, and reduces its ionization level, with the advantageous result that a relatively smaller heat sink can be employed therein.
An aspect of the present invention is to provide an exhaust control device of a relatively small size.
Another aspect of the invention is to provide an exhaust control device having multiple expansion chambers therein for reducing the peak intensity of a blast of gases from a circuit interrupter.
Another aspect of the present invention is to provide an exhaust control device having a first expansion chamber substantially interposed between an inlet and a heat sink of the exhaust control device, and additionally includes a second expansion chamber that is aligned with the inlet, whereby a meaningful portion of a blast of gases being received through the inlet will be directly received in the second expansion chamber to reduce the peak intensity of the blast gases passing through the heat sink.
Another aspect of the present invention is to provide an exhaust control device that can be manufactured relatively less expensively without reducing the overall effectiveness thereof.
Another aspect of the present invention is to provide an exhaust control device that reduces the temperature, velocity, and ionization level and of gases produced in a circuit interrupter upon interruption of a circuit.
Accordingly, an aspect of the present invention is to provide an exhaust control device for use in conjunction with a circuit interrupter, in which the general nature of the exhaust control device can be stated as including a casing having an interior and including an inlet and an outlet in flow communication with the interior, with the inlet being structured to be connected in fluid communication with the circuit interrupter, a support apparatus disposed within the interior, a wall disposed within the interior of the casing and mounted on the support apparatus, a porous heat sink disposed within the interior of the casing between the inlet and the outlet and extending at least partially around the wall between the wall and the casing, with the heat sink being structured to permit the flow of fluid therethrough, a first expansion chamber disposed within the interior at least partially between the inlet and the heat sink, the first expansion chamber having a greater cross-sectional area than the inlet, and a second expansion chamber defined by the wall and in fluid communication with the first expansion chamber, the second expansion chamber having a mouth that is in register with at least a portion of the inlet.
The second expansion chamber of such an exhaust control device may be centrally disposed within the heat sink.
The support apparatus may include a perforated upstream plate and a perforated downstream plate, with the wall and the heat sink being substantially interposed between the upstream and downstream plates. In such an exhaust control device, the support apparatus may additionally include a fastener that extends between the upstream and downstream plates and extends through the expansion chamber. Alternately, or in addition thereto, the downstream plate may include a non-perforated portion that is engaged with the wall and that at least partially defines the second expansion chamber, with the non-perforated portion being disposed opposite the mouth of the second expansion chamber.
Still another aspect of the present invention is to provide an exhaust control device for use in conjunction with a circuit interrupter, in which the general nature of the exhaust control device can be stated as including a casing having an interior and including an inlet and an outlet in flow communication with the interior, with the inlet being structured to be connected in fluid communication with the circuit interrupter, a support apparatus disposed within the interior of the casing, a porous heat sink disposed within the interior of the casing between the inlet and the outlet, with the heat sink being structured to permit the flow of fluid therethrough, a first expansion chamber disposed within the interior at least partially between the inlet and the heat sink, and a second expansion chamber disposed inside the heat sink and being in fluid communication with the first expansion chamber. The second expansion chamber may include a mouth that is in register with at least a portion of the inlet.
Such an exhaust control device may include a heat sink that is substantially annular in cross-section and is formed with a substantially cylindrical central cavity, with the second expansion chamber being disposed in the central cavity. Additionally, the support apparatus may include an annular wall disposed within the central cavity, with the second expansion chamber being disposed within the wall. Additionally, the wall may extend about a central axis, whereby the central axis extends through the inlet of the exhaust control device.